Alighting gear for aircraft



April 9, 1940. r. H. STONE ALIGHHNG GEAR FOR AIRCRAFT Filed Au 8, 1939 2 Sheets-Sheet 1 Patented Apr. 9,1940

ALIGHTING GEAR FOR Theodore Handley Stone, Singapore, Straits 1 Settlements r Application August 8,

1939, Serial No. 289,084

In Great Britain August 2, 1938 5 Claims, '(Cl. 244-401) This invention relates to alighting gear for aircraft and is particularly concerned with aircraft of the flying boat kind, 1. e., one having a buoyant hull or fuselage. The invention seeks to provide landing gear so that the aircraft may be used as an amphibian, being capable of landing on and taking-off from both land and water aerodromes.

Aircraft of, the flying boat kind are known in which wheel undercarriages are provided, enabling them to operate fromland aerodromes, such undercarriages being supported by the fuselage or hull and/or wing structure, and being retractable so as-to enable the wheels to be raised clear of the water to permit the aircraft to operate thereon. Further, it has been proposed to provide aircraft of the seaplane'kind, in which buoyant floats are utilised to support the aircraft fuselage clear of the water surface, with wheels retractively accommodated within the floats, enabling the aircraft to operate as an amphibian, both on land and water.

In accordance with the present invention an amphibian aircraft of the flying boat kind is provided with stabilising floats into which landing wheels are partly or wholly retractable, .the wheels when extended projecting below the level of the hull so as to enable the aircraft to land and take off from a land aerodrome, and the float-supporting structure being capable of supporting the entire weight of the aircraft and being adapted to resist landing loads, when the aircraft is used as a land-plane. By the term "stabilising floats is meant floats disposed at each side of the hull of a flying boat below the wing structure and supported partly or wholly thereby, and arranged by their buoyancy to maintain or assist in maintaining the transverse stability of the aircraft. Retraction may conveniently be effected by fluid pressure jack means arranged to cause swinging of a wheel mounting about a pivot hearing within a recess in the under surface of a stabilising float, and in order to'enable landing wheels of comparatively small diameter to be used, whereby they can be accommodated within the float, the wheels may be arranged in tandem. The retraction of the wheel landing. gear preferably effects simultaneous or subsequent closure of a door to the recess, and the door may form a water-tight closure, preventing immersion of the landing wheels and in effect increasing the buoyancy of the float.

The invention is illustrated diagrammatically in the accompanying drawings, showing its application to a flying boat of the high wing monoplane kind about one third of the way the drawings- Figure l is a front elevation of the flying boat showing the wheel undercarriage ,extended in dotted lines;

Figure 2 is a detail view in part section of a stabilising float showing the wheel landing gear accommodated therein in the retracted condition;

Figure 3 is a view similar to that of Figure 2 with the wheel undercarriage extended; and

Figure 4 is a detail view of a valve arrangement suitable for effecting locking of the undercarriage in the retracted condition.

Referring to Figure l, the flying boat has a buoyant hull III with a wing structure ll supporting engines l2. The aircraft as shown is of the monoplane kind and below the wing on each side of the hull. It a stabilising float I3 is mounted on shock-absorber struts l4. Each float I3 is along the span. In

further connected-with the wing it by struts IS. The stabilising floats l3, whilst providing some buoyancy supporting the weight of the aircraft on the water, are primarily provided for the purpose of maintaining or assisting in maintaining the transverse stability of the flying boat, and for this purpose are generally placed sufliciently along the span of the wing to provide an adequate moment for maintaining the hull on an even keel in the transverse sense. The line W-L in Figure -1 shows the water line, with the aircraft supported by the -buoyancy of the hull l0 and stabilising floats 13 on water, whilst the ground line G-L in Figure 1 shows the attitude of the aircraft when supported by the wheel landing gear generally shown at IS in dotted lines. The wheel landing gear I6 is capable of being retracted so as to be accommodated within the floats l3, for the purpose of reducing air drag of the parts and also to enable the flying boat to land on and take off from water. i

In Figures 2 and 3 there is shown in detail a stabilising float l3 having a recess ll, formed with an opening in its underside serving to accommodate retraction gear and the wheels and wheel mounting when retracted. Wheels It as seen in Figure 1 are supported in tandem on a mounting l9 which may comprise any known or convenient shock-absorbing means, if shock-absorbing, in addition to that provided by the struts I4,

is desired. The mounting i9 is carriedabout av main pivot in a bearing structure II adapted,

to transmit landing leads directly to the shockabsorber struts It by which the float I3 is carwith the stabilising floats situated ried on the wing The journal 2|A of the bearing structure 2| is in the form of an elongated slot permitting a certain degree of movement of the pivot in the vertical sense against resilient resistance aflorded by a spring diagrammatically shown at 22 (see Figure 2). A slot 23 in the structure 2| is formed as a circular arc about the pivot axis when the spindleis in its lowermost position in the elongated journal bearing, and a transverse pin 24 carried on a prolongation of the mounting |9 beyond the pivot 20 engages this arcuate formation, which is conveniently duplicated so as to provide one on each side of the mounting. Under ground load with the wheels I8 extended, the spring 22 is compressed so that the pin 24 enters extensions 25 of the slots 23 in the vertical sense, whereby the mounting is ef- 'fectively locked against angular movement.

When the wheels l8 are relieved of ground load the spring 22 urges the pivot spindle downwardly to disengage the pin 24 from the slot extensions 25, whereafter the mounting is free to swing about the pivot 20, the pin 24 being guided in the arcuate slots 23.

The mechanism for effecting retraction comprises a pair of hydraulic double-acting piston and cylinder jacks 26 with an associated hydraulic lock 21 arranged in series. The jack cylinder is pivotally mounted at 28 on the bearing structure 2|, whilst the outer extremity ,of the piston rod is pivoted to the transverse pin 24. Introduction of hydraulic pressure to the appropriate side of the piston causes angular movement of the mounting l9 about the pivot bearing 20 so as to extend and retract the wheels l8. The hydraulic pressure 'to each jack is supplied by pipelines 29 and 29A from a reversible source, and the locking device 21 is interposed in the pipe of the undercarriage.

The locking device 21 shown in detail in Figure 4 comprises a cylinder 30 within which operates a hollow piston 3|, integral with which is a locking pin 32. The lower end of the cylinder is closed by a wall 33 in screwed engagement with the cylinder 30, and providing a sleeve portion 34 the upper end 35 of which forms a stop limiting the downward movement of the piston 3|. Within the sleeve portion 34 there operates a piston device 36 guided on a piston rod 31 within the wall 33, and resiliently urged by a spring 38 in the upward direction. The piston 36 thus forms a yieldable wall to the cylinder 30. A compression spring 39 interposed between the piston 36 and the piston 3| urges the locking bolt 32 in an upward direction, into a position where it locks the wheel mounting IS in the retracted condition. For extension of the wheel mounting, liquid under pressure is introduced through the pipeline 29 to the port 40 at the upper end of the cylinder 39, and this acting on the piston 3| depresses the locking bolt 32 by compressing the spring 39 and displacing liquid from underneath 'the piswhich forms a branch ton 3| throughia port 4| of a conduit 42,leading by pipeline 43 (see Figures *2 and 3) to the jack 26. Pressure on top of the piston 3| depresses it until its upper edge 44 aligns with the port 45, which constitutes-a second branch of the conduit 42. There isthen free passage of liquid from the pressure source through the port 40; port 45 and conduit 42 to the jack 26, so as to operate the piston and cause the wheel mounting to swing from the position shown in Figure 2 to that of Figure 3. It will be appreciated that until the bolt 32 releases the piston 24 to allow it to slide in the arcuate slots 23 appropriate for extension the piston of the jack 26 is not free to move, and further that the overlap of the piston 3| closes the port 4| during depression before the port 45 is open to'the port 40; the yielding wall 36 accommodates for liquid trapped below the piston-3| during depression, especially after the port 4| is cut oil. The upper edge 35 of the sleeve portion 34 forms a stop limiting the downward movement upwards after completion of undercarriage extension, leaves the port 4| open so that liquid from k the jack 26 acting on the underside of thepiston 3| raises the ball valve 46 accommodated within the hollow of the piston 3|. This ball valve is spring-urged to the closed position by a compression spring 41. The, liquid displaced by the piston of the jack 26 thus passes back through the conduit '42, port 4|, through the hollow of the piston 3| to the port 40 and thence back to the reservoir of the pressure system by way of pipeline 29. At the completion of retraction the pin rides on a ramp formation 48 at the extremity of the bolt 32, whereafter the bolt is springurged into the locked condition.

In Figures 2 and 3 a hinged door is illustrated for closing the compartment -This closureindicated at 49 is hinged at 59 to the float I3 and connected through a pair of pivoted links 5| to the wheel mounting l9. It will be appreciated .that during swinging of the wheel mounting I9 ing l9 to pass over the dead centre, and con-- tinued movement effects closing of the door 49.

If desired the links 5| may be telescopically extensible against resilient resistance, so that final retraction movement actually applies a tension in the links, the door having come up against a stop, whereby anefiective seal may be provided. There is preferably also a non-return valve in the bottom of the recess permitting water to flow out from the space in which the ports are retracted, but preventing in-flow; this valve would presumably be placed at the step of float 3 where suction during take-01f from water would extract any water that might have entered chamber ll. It will be appreciated that since the links 5| swing relative'to the mounting |9 across the axis of rotation of the wheels I 8, it is necessary that these links lie outside the planes of the wheels. The pivot axis 53 is thus constituted by a cross bar element extending transversely and fixed to the mounting I9.

It is, of course, to be understood that the floatsupporting structure I4, I 5, etc., is constructed as asuflicient structure to withstand all normal landing loads and the weight of the aircraft. Thus the stabilising floats and their attachment to the aircraft can be looked upon as constituting the main undercarriage elements when the aircraft is in use as a landplane. It will be appreciated that there must be suiflcient clearance afforded between the hull II and the groundline for the shock absorber and tyre deflection which may occur when the aircraft is groundborne.

What I claim is:

1. Means for looking a pivotally mounted retractable landing gear against pivotal movement while the landing gear is in projected position and the weight of the aircraft is taken thereby comprising, a landing element, a supporting element therefor, means for pivotally attaching the landing element to .the supporting element, said means including a journal defining a generally vertical path for reciprocation and an axle reciprocal therein, and latching means including adjacent members fixed on said elements, said members being relatively movable in a reciprocating path controlled by said pivotal attaching means into latching engagement upon-relative reciprocal movement of said elements in response to the assumption of the weight of the aircraft by said landing elements and out of latching engagement to permit relative pivotal-movement of said elements as the aircraft is otherwise supported.

2. Means for locking a pivotally mounted retractable landing gear against pivotal movement while the landing gear is in projected, position and the weight of the aircraft is taken thereby comprising, a landing element, a supporting ele-e ment therefor, means for pivotally attaching the.

landing element to the supporting element, said means including a journal defining a generally vertical path for reciprocation and an axle reciprocal therein,- latching means including adjacent members fixed on said elements, said members being relatively movable in a reciprocating path controlled by said pivotal attaching means into latching engagement upon relative reciprocal movement of said elements in response to the assumption of the weight of the aircraft by said landing elements and out of latching engagement to permit relative pivotal movement of said elements as the aircraft isotherwise supported, and a spring mounted in said Journal in engagement with said axle for normally 1118 1 2 the axle toward the bottom of said Journal.

3. A retractable landing gear for aircraft comprising, a support attached to the aircraft. a

landing element pivoted to said support, a Jack pivoted to said support andincludlng an exfor said am in extended position, means on'said support operable upon said arm for locking the same in retracted position, means in said sup- 5 port defining a guideway for said arm to control its reciprocating path and to guide the same from one lock to the other, and means for oper-. ating said jack to extend said arm to move said landing element to and from a landing position.

4. An amphibious aircraft of the flying boat type having a buoyant landing, member, mountings supported within said buoyant member, a retractable ground landing element pivotally attached to said mounting for movement to and from a position wholly within said buoyant member, a hydraulic jack having an extensible arm attached to said ground landing element, a lock operable upon said arm and associated with said Jack to effect the locking of said am in fixed position when the latter. is retracted, closure means associated with said buoyant member and movable to permit the projection of said ground landing element, said closure means being attached to said ground landing element and adapted to be moved thereby upon full retraction thereof to a position to seal said buoyant memberwithin said journal and a stud adapted to 00- operate with said slot in one position of said axle in said Journal to lock said supporting element and said landing element against relative movement, meansfor projecting and retracting said ground landing element to and from a position within said float about said journal as an axis, a spring mounted in said journal and operable upon said axle for urging the same to a position within the Journal where said stud and slot do not cooperate, said spring being compressed when the aircraft is supported on said landing element thereby locking the same in landing position, while an automatic release of said lock is eflected by the action of said spring when the aircraft is otherwise supported. 

